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Topic: Voltage is dropping (Read 529 times) previous topic - next topic

Voltage is dropping

Good evening everyone,
Maybe I should say losing voltage.
I recently installed a VE multiplus which has not been working properly.
I started to take some voltage readings and on the input side for the inverter charger voltage is dropping quickly from 120's  down to the 60s.
I backtrack to the main circuit breaker box located at the face of the bed and the same situation was happening at circuit breaker number eight. No circuits are tripping the breakers.
I checked the 50 amp line coming in to the main circuit breaker box and had the same results.
Next I cut the short power and turned on the generator and had the same issue.
all A/C's residential fridge and microwave  are working properly. Incoming voltages are 126 and 123.
Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH

Re: Voltage is dropping

Reply #1 –
Do you have a shore power reel?  If so, check the contacts.

If not, check shore power cord (that much voltage drop will likely cause HEAT and discoloration), as well as wiring to ATS, inside connections in ATS and connections inside the main 120 VAC breaker box.

Actually, all those places should be part of an annual preventive maintenance check, so not really a waste of time.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Voltage is dropping

Reply #2 –
Wiring to both ATS looks good and is not hot.
I ran the gen and had the same results.
Checked wiring at the breaker panel at foot of bed.looks good
Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH

Re: Voltage is dropping

Reply #3 –
Frank, make sure your main panel circuit breaker panel breaker for the multiplus in on. 

Charging the batteries using the Multiplus requires only that circuit breaker to be on and 120v available and wired correctly to the multiplus.

Is the multiplus ON?  If it is and is charging your voltage should be close to 13.4-13.8 volts.  What you are seeing says it is not charging.  No 120v or not on or a failed big 350 amp fuse or some other wiring error.

What is the voltage on the 12v cables at the multiplus?  What ic the voltage at the batteries?
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Voltage is dropping

Reply #4 –
Quote from: Lt403 –
Good evening everyone,
Next I cut the short power and turned on the generator and had the same issue.
all A/C's residential fridge and microwave  are working properly. Incoming voltages are 126 and 123.

It sounds like a bad connection in the transfer switch, and that's only of you A/Cw, fridge and microwave are on one leg of the incoming.

Pull and replace circuit breaker number 8, with a new breaker, paying attention to where it snaps into the buss bar.

60VAC voltage drop is a lot of heat some where at that amount of current.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Voltage is dropping

Reply #5 –
Quote from: Old Toolmaker –
60VAC voltage drop is a lot of heat some where at that amount of current.


Yes, this is the CRITICAL ISSUE.  Could be a fire hazard.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Voltage is dropping

Reply #6 –
Voltage is also not an absolute measurement; it is a RELATIVE DIFFERENCE measurement - how many volts HIGHER than reference the hot conductor measures.  If there is current flowing in the same direction on the reference conductor, the relative difference when you meter the HOT relative to that reference will be less than if that current weren't there.

Don't automatically assume the issue is a poor connection with HOT or that you have resistance heating losses.  It can easily be a loose neutral or ground connection or power flowing where it shouldn't be.  The latter particularly when you are seeing that much discrepancy.  Safely disconnect from all power and inspect, clean, and tighten all connections.

Since you mentioned the inverter/charger being a recent addition and not working correctly, are you absolutely sure it is wired in correctly?  We have seen whacky voltage readings when something miswired was connected to campground shore power.  In your case, since it happens on both shore and generator, it points to something in your coach. 

If this voltage behavior is coincident with the new inverter installation, be highly suspect of that installation/unit.  In particular, verify the wiring in of the inverter to the coach.

Note that if there is a miswire and you are getting current flowing on the A/C ground conductors, you have a very serious safety issue that can result in "hot skin".
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Voltage is dropping

Reply #7 –
You have 2 sets of breakers. One set is inverted and the other set is NOT inverted appliances. You have to determine if the inverted side is working 100% and if the non inverted side is working 100%. If the inverted appliances (plugs and whatnots) are not 120 you have a problem with your inverter or related transfer switch if the non inverted side is working ok.
1994 U280, Build 4490
Deming, NM.

Re: Voltage is dropping

Reply #8 –
Just to clarify, you have the same voltage drop on shore and generator power? Or just on the inverter power, with no other power ( shore or generator) connected?
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Voltage is dropping

Reply #9 –
Quote from: Michelle –
Note that if there is a mis-wire and you are getting current flowing on the A/C ground conductors, you have a very serious safety issue that can result in "hot skin".

I am a one hand in the pocket kind of guy when it comes to electricity, so I have an alligator clip on my Fluke's negative lead.  It gets connected to a good earth ground, or the next best thing that I can find.  This morning it was a negative battery terminal on the source battery.  Voltage is where it appears.  Then you have to find out why. 

LT403 wrote;

"I recently installed a VE multiplus which has not been working properly."

As good a place to start as any.  Did you install a chassis ground for the frame of the inverter?

"I started to take some voltage readings and on the input side for the inverter charger voltage is dropping quickly from 120's  down to the 60s."

Dropping quickly indicates a local problem without much current.


"I backtrack to the main circuit breaker box located at the face of the bed and the same situation was happening at circuit breaker number eight. No circuits are tripping the breakers."

I still say check the #8 circuit breaker by swapping in a known good part and examining the buss connection.  Might and well tug on all the commons while you're in there.

"I checked the 50 amp line coming in to the main circuit breaker box and had the same results."

Did you check against the earth ground, the green wire?

"Next I cut the shore power and turned on the generator and had the same issue."

The caller is in the house.  In my mind the generator should be earth grounded to the chassis so check an be certain that the 110VAC commons aren't floating above the chassis.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Voltage is dropping

Reply #10 –
Thanks everyone,
I found a blown 350 A fuse to the house batteries, should be here Tomorrow. Started and ran the coach and the house batts were charging.

I was getting the same V loss on both shore and gen power

I will continue to check for the voltage loss as suggested . Starting at the pedestal and working in.

Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH

Re: Voltage is dropping

Reply #11 –
Quote from: Lt403 –
I will continue to check for the voltage loss as suggested . Starting at the pedestal and working in.

Do you have an easy means of isolating the inverter from the coach wiring?  If there is 120 VAC power feeding into it (for battery charging purposes), can you shut off the breaker (on the main panel) that feeds it 120 VAC?  If so, do your metering with that breaker on and off.  Is there a difference?

If this voltage issue has shown up coincidentally with the new inverter, suspect the inverter or its installation.

ETA - Circuit breaker #8 is the breaker that feeds 120 VAC FROM the main supply (shore or generator) TO the inverter to charge the batteries.  To me, it sounds like the inverter is possibly miswired to this circuit (or has an internal wiring defect) and/or is feeding/routing current back on either neutral or ground, which is causing you do only read half voltage.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320
 

Re: Voltage is dropping

Reply #12 –
Thanks to everyone that responded.
Started to check at the pedestal and same thing.
Went to 2 more pedestals with same results.

Borrowed a meter from my neighbor at the RV park and performed the same measurements with no loss of voltage.

I always check my meter with a continuity test before starting.

Bought a new meter 😊 no more voltage loss.

Now I am waiting for my new 350A fuse which should be here tomorrow.
Frank & Daisy
NO LONGER  "looking for the perfect Foretravel
36' or less non slide preferred."  She has been found and is ours.
2003 U320 36' non slide  Unit 6103
Cummins ISM 450
Allison 4000MH